Method and system for evaluating reliability of rubber and plastic watertight connector

Abstract

The invention discloses a rubber and plastic watertight connector reliability prediction method and an evaluation system, which are used for predicting the future reliability state of a test piece according to test data obtained by different test pieces under a specific test profile based on different key design factors. The reliability prediction method comprises the steps of obtaining a contact resistance initial value of a test piece and obtaining a contact resistance measured value of the test piece in each cycle test period, calculating a contact resistance degradation amount through the contact resistance initial value and the contact resistance measured value, and analyzing the obtained related data to obtain a reliability prediction result. A prescribed function is used to derive a formula representing a fitted curve of the marker. Reliability evaluation of the rubber and plastic watertight connector is carried out through the method, and improvement of key design factors corresponding to weak links of a product can be reversely guided according to an evaluation result.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber and plastic wet pluggable connectors, and particularly relates to a reliability evaluation method and an evaluation system for rubber and plastic watertight connectors. Background Art

[0002] In recent years, while the overall reliability level of military equipment has been greatly improved, the reliability index requirements for some products and equipment have also become higher and higher. As an important product type in military products, the rubber and plastic watertight connector can be directly plugged and unplugged in a shallow water environment, has independent sealing and longitudinal sealing functions, and can transmit signals underwater. As an important component for the normal operation of underwater equipment, the waterproof connector is used more and more widely, mainly serving the offshore oil platform, navy, marine geophysics and marine scientific research markets. These actual application environments and functional requirements require the rubber and plastic watertight connector to have a high reliability level. However, there are technical difficulties such as watertight performance, insulation performance, and pressure resistance performance in the existing rubber and plastic connectors. Therefore, carrying out the reliability evaluation work of rubber and plastic watertight connector products can verify whether the products can be directly applied in practice, so as to provide directions and references for the design improvement of the products. However, in the related existing technologies, there is still a lack of a scientific and reasonable reliability evaluation method for rubber and plastic watertight connectors. Summary of the Invention

[0003] The purpose of the invention is to solve the problems existing in the above-mentioned prior art, and provide a reliability evaluation method and an evaluation system for rubber and plastic watertight connectors. This method is improved based on potential failure analysis and key design factors, determines the weak links of the product through FMECA (Failure Mode, Effects and Criticality Analysis), analyzes the failure mechanism for the weak links, and determines the reliability test profile according to the actual use environment. By simulating the actual use environment of the product, the accuracy of the evaluation result is higher and the result is more credible. Through the reliability evaluation of the rubber and plastic watertight connector carried out by this method, according to the evaluation result, it can inversely guide the improvement of the key design factors corresponding to the weak links of the product.

[0004] To achieve the above purpose, one of the purposes of the invention is to provide a reliability evaluation method for rubber and plastic watertight connectors, which predicts the future reliability state of the product test piece based on the test data obtained by the product test piece under a specific test profile according to different key design factors. The reliability evaluation method includes: obtaining the initial value of the contact resistance of the product test piece and obtaining the measured value of the contact resistance of the product test piece in each cycle test period, calculating the contact resistance degradation amount through the initial value of the contact resistance and the measured value of the contact resistance, and marking and analyzing the characteristic parameters of the product test piece based on different key design factors and the obtained corresponding relevant data, and using a specified function to derive an expression representing the marked fitting straight line or fitting curve.

[0005] As a preferred solution, the reliability state of the future product test piece is predicted based on the test data obtained respectively under their respective specific test profiles for two key design factors, namely the plating thickness of the contact piece of the product test piece and the rib seal dimension at the mating part of the product test piece; the initial values of the contact resistance of all product test pieces are obtained, and all grouped product test pieces are put into a simulated test solution according to the key design factors and in accordance with the corresponding set test profile to carry out a cyclic test. After each cycle test is completed, the next cycle test is continued until the product test piece fails or reaches the failure threshold of a given contact resistance degradation amount.

[0006] As a preferred solution, in the reliability evaluation method;

[0007] For the plating thickness factor of the contact piece;

[0008] By obtaining the initial value of the contact resistance and the measured value of the contact resistance, the contact resistance degradation amount is calculated, the contact resistance degradation amount and the characteristic life value of the product at different plating thicknesses are obtained, the contact resistance degradation amount and the cycle number are marked and analyzed, and the contact resistance degradation amount and the characteristic life value are fitted with a linear function to derive the expression representing the fitted straight line;

[0009] Based on the failure threshold of the given contact resistance degradation amount,

[0010] The characteristic life values corresponding to different plating thicknesses are calculated according to the above expression of the fitted straight line;

[0011] By marking and analyzing the different plating thicknesses and the corresponding characteristic life values, and fitting the plating thickness and the corresponding characteristic life values with a logarithmic function, the expression (1) representing the fitted curve is derived;

[0012] Through the above expression of the fitted curve, the characteristic life value when the product reaches the failure threshold of the contact resistance degradation amount at different plating thicknesses can be calculated; thus, the appropriate plating thickness is selected according to the product grade requirement, and the reliability prediction and evaluation of the product based on the plating thickness are completed accordingly.

[0013] As a preferred solution, the characteristic life is the number of cycles.

[0014] As a preferred solution, in the reliability evaluation method;

[0015] For the rib seal dimension factor at the mating part, the compression rate of different rib seal dimensions is calculated;

[0016] By obtaining the initial value of the contact resistance and the measured value of the contact resistance, the contact resistance degradation amount is calculated; the test time of the product at different environmental temperatures under different compression rates is obtained;

[0017] By performing data marker analysis on the test time and the corresponding contact resistance degradation amount at different environmental temperatures with different compression ratios, and fitting the test time and the contact resistance degradation amount with a power function, an expression representing the fitting curve is derived;

[0018] Through the above expression, the calendar life value of the product can be calculated based on a specific environmental temperature under the failure threshold of a given contact resistance degradation amount;

[0019] Substitute the specific environmental temperature and the calendar life value into the acceleration model to obtain the relationship expression (2) between the environmental temperature and the calendar life value at different compression ratios;

[0020] Through the above relationship expression (2), the calendar life values of the product at different environmental temperatures with different compression ratios can be calculated;

[0021] By comparing the characteristic life values of the products with different compression ratios at a specific environmental temperature, an appropriate compression ratio is selected to complete the reliability prediction and evaluation of the product based on different rib seal dimensions;

[0022] As a preferred solution, according to the reliability prediction and evaluation results based on the coating thickness and the reliability prediction and evaluation results based on different rib seal dimensions, the corresponding reliability prediction and evaluation results can be used as the conclusion based on different usage requirements, or the earlier of the two reliability prediction and evaluation results can be used as the final reliability prediction judgment standard for the product;

[0023] As a preferred solution, the expression (1) is represented as:

[0024] N = aln(THK) + b (1)

[0025] In formula (1), N is the characteristic life of the rubber water seal connector; THK is the coating thickness of the contact; a and b are constants obtained when deriving the expression of the fitting curve;

[0026] As a preferred solution, the expression (2) is represented as:

[0027]

[0028] In formula (2), L x is the calendar life of the rubber and plastic water-tight connector when the sealing compression ratio is x; T is the environmental temperature value, and a and b are constants obtained when deriving the expression of the fitting curve;

[0029] The second object of the present invention is to provide a reliability evaluation system for a rubber and plastic water-tight connector, which predicts the reliability state of the future product test piece based on the test data obtained from different test pieces under specific test profiles according to different key design factors. The reliability prediction system includes:

[0030] It includes a contact resistance detection unit, which is used to obtain the initial value of the contact resistance of the product test piece and the measured value of the contact resistance of the product test piece in each cycle test period.

[0031] A contact resistance degradation amount calculation unit, which is used to calculate the contact resistance degradation amount through the initial value of the contact resistance and the measured value of the contact resistance.

[0032] An equation derivation unit.

[0033] Regarding the plating thickness factor of the contact part of the test piece.

[0034] By data - marking and analyzing the contact resistance degradation amount and the number of cycles, and fitting the contact resistance degradation amount and the characteristic life value with a linear function, an equation representing the fitting straight line is derived.

[0035] Based on the given failure threshold of the contact resistance degradation amount.

[0036] According to the equation of the above - mentioned fitting straight line, the characteristic life values corresponding to different plating thicknesses are calculated.

[0037] By data - marking and analyzing different plating thicknesses and the corresponding characteristic life values, and fitting the plating thickness and the corresponding characteristic life value with a logarithmic function, an equation (1) representing the fitting curve is derived.

[0038] Regarding the rib sealing size factor of the mating part of the test piece.

[0039] Obtain the test time of the product at different environmental temperatures under different compression ratios.

[0040] By data - marking and analyzing the test time at different environmental temperatures under different compression ratios and the corresponding contact resistance degradation amount, and fitting the test time and the contact resistance degradation amount with a power function, an equation representing the fitting curve is derived.

[0041] Through the above - mentioned equation, the calendar life value of the product based on a specific environmental temperature under the given failure threshold of the contact resistance degradation amount can be calculated.

[0042] Substitute the specific environmental temperature and the calendar life value into the acceleration model to obtain the relationship equation (2) between the environmental temperature and the calendar life value under different compression ratios.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] This method provides a reliability evaluation method for rubber and plastic waterproof connectors. First, FMECA is carried out for rubber and plastic waterproof connectors. According to the FMECA results, the weak links in the use process of rubber and plastic waterproof connectors are located as the increase in contact resistance caused by wear and corrosion of metal contacts. Reliability tests based on the coating thickness of the contacts and the rib seal size at the mating part are carried out for the weak links. According to the test data analysis, the influence of the coating thickness of the contacts and the rib seal size at the mating part on the product performance degradation is analyzed, and a performance degradation model is established. Based on the degradation model, the product life level is predicted to realize the reliability evaluation of rubber and plastic waterproof connectors. Through the reliability evaluation of rubber and plastic waterproof connectors carried out by this method, according to the evaluation results, the improvement of the key design factors corresponding to the weak links of the product can be guided in reverse. By carrying out the reliability evaluation based on the key design factors of the coating thickness of the contacts and the rib seal size, according to the different use requirements of the product, the corresponding evaluation data are used as the conclusion, or the reliability evaluation result with a shorter calendar life is selected as the reliability evaluation of the product. Since the two evaluation models correspond to two key design factors, through this method, the reliability levels under different levels of the two key factors of the coating thickness and the rib seal size can be determined, and the appropriate design values can be selected accordingly, so as to effectively provide an improvement direction and suggestions for the product design. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 It is a schematic diagram of the reliability evaluation process of the rubber and plastic waterproof connector of the present invention;

[0047] Figure 2 It is a schematic diagram of the test profile of the reliability test for the coating thickness of the contacts in the present invention;

[0048] Figure 3 It is a schematic diagram of the test profile of the reliability test for the rib seal size in the present invention;

[0049] Figure 4 It is a schematic diagram of the plug pins and jacks before mating of the rubber and plastic waterproof connector of the present invention;

[0050] Figure 5 It is a table graph of the fitting degradation model of the contact resistance at different temperatures with different compression ratios in the present invention;

[0051] Figure 6 It is a table graph of the calendar life based on the degradation model in the present invention;

[0052] Figure 7 This is the fitting diagram of the reliability test model for the convex rib sealing dimension in the present invention: Test piece: Compression ratio is 3%; Fitting diagram of the model at an ambient temperature of 70°C;

[0053] Figure 8 This is a process photo of implementing the reliability evaluation method for the rubber and plastic waterproof connector of the present invention;

[0054] Figure 9 This is a schematic diagram of the reliability evaluation system for the rubber and plastic waterproof connector in the present invention;

[0055] Markings in the figure: 1. Pin component, 10. The volume of the part shown in the rectangular box is V 插针 , 11. Pin contact, 2. Jack component, 20. The volume of the part shown in the rectangular box is V 插孔 , 21. Jack, 22. Convex rib, 23. Vulcanized main body. Specific embodiments

[0056] The present invention will be specifically described below through exemplary embodiments. However, it should be understood that without further elaboration, the elements, structures, and features in one embodiment can also be beneficially combined with those in other embodiments.

[0057] It should be noted that: Unless otherwise defined, the technical terms or scientific terms used herein should have the ordinary meaning understood by those of ordinary skill in the art to which the present invention pertains. The words such as "a", "one", or "the" used in the specification and claims of this patent application for the present invention do not express a limitation in quantity, but rather indicate the existence of at least one. Words such as "comprising" or "including" point out that the elements or objects appearing before "comprising" or "including" cover the elements or objects listed after "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same function.

[0058] As shown in the figure, this embodiment provides a reliability evaluation method for a rubber and plastic waterproof connector, including the following steps:

[0059] Step 1: Determine the key design factors of the potential failure modes of the rubber and plastic waterproof connector according to the actual use conditions, including the contact plating thickness and the convex rib sealing dimension at the mating part;

[0060] In this step, the potential failure modes of the rubber and plastic watertight connector are determined according to the actual operating conditions, and FMECA is carried out on the rubber and plastic watertight connector. It is identified that the potential failure mode of the rubber and plastic watertight connector is mainly the increase in contact resistance. The main reasons for the increase in contact resistance are as follows: (1) caused by the corrosion of metal contacts in the marine environment; (2) the contact parts are worn due to long-term plugging and unplugging at the sealing position of the rib in the pinhole. For reasons (1) and (2), we analyze that they are related to the design factor of the coating thickness of the contact part (the outer surface of the contact part indicated at 11 in the figure is the coating of the contact part) and the design factor of the rib sealing size at the mating part. That is, by selecting an appropriate design thickness, it can effectively avoid the increase in the contact resistance of the connector caused by the seawater corrosion of the metal contact part in the marine environment, thus providing effective guidance for the product improvement direction; by making a suitable design selection according to the rib sealing size at the mating part, it can effectively avoid the increase in the contact resistance of the connector caused by the wear of the contact part due to long-term plugging and unplugging, thus providing effective guidance for the product improvement direction. Therefore, in this first step, the key design factors of the rubber and plastic watertight connector are determined as: the coating thickness of the contact part and the rib sealing size design at the mating part.

[0061] Step 2: Determine the reliability test plan for different key design factors; before the reliability test, perform performance tests on all product test pieces and record the initial value of the contact resistance, and establish a test profile by simulating the actual underwater use task; group the product test pieces according to different key design factors, and after grouping, put all the grouped product test pieces into the simulated test solution according to the corresponding set test profile to carry out a cyclic test. After each cyclic test is completed, take out the product test pieces from the simulated test solution and test their contact resistance and record the measured value of the contact resistance; after each cycle of the test is completed, continue with the next cyclic test until the product test pieces fail or reach the specified cut-off condition to terminate the test.

[0062] In this second step, reliability tests are carried out respectively for the two key design factors of the coating thickness of the contact part and the rib sealing size at the mating part.

[0063] The reliability test plan for the comparison group for the coating thickness of the contact part is as follows:

[0064] As Figure 2As shown, this test plan establishes a test profile by simulating the actual underwater use mission, namely the "underwater static - underwater power on - plug and unplug" cycle. The main stresses in the test conditions are the (sea) water environment, electrical stress (rated current), and plug - and - unplug mechanical stress (the plug - and - unplug mechanical stress mainly means that during the test profile, the product test piece is plugged and unplugged underwater, which will accelerate the wear of the test piece plating and the aging of rubber). The test pieces are grouped according to the plating thickness, and after grouping, all grouped test pieces (connectors) are placed in the simulated test seawater according to the test profile to carry out the cyclic test. After each cycle is completed, the test piece needs to be taken out of the simulated test seawater for contact resistance testing and data recording. After the testing is completed, the next cycle test continues. Specifically, in this embodiment, underwater static without power - underwater power on - underwater plug and unplug 10 times without power can be used as a cycle.

[0065] Reliability test for the rib seal size at the mating part:

[0066] Since the test period is long and the cost is high at room temperature, the high - temperature accelerated test method is adopted to shorten the reliability test period. For example, in the high - temperature accelerated test, the test specimens are divided into three groups and tested in high - temperature environments of A℃, B℃, and C℃ respectively, as Figure 3 shown. The test simulates adding high - temperature stress as the accelerating stress under the conventional use requirements of the product to establish a test profile, that is, the process of "high - temperature (three temperatures A℃, B℃, C℃) aging without power - underwater power on - underwater plug and unplug - underwater static". The main stresses in the test conditions are high temperature, air (oxygen), (sea) water environment, electrical stress (rated current), and plug - and - unplug mechanical stress. The test pieces are grouped according to the rib seal size, and after grouping, all grouped test pieces (connectors) are placed in the simulated test solution according to the test profile to carry out the cyclic test. After each cycle is completed, the test piece needs to be taken out for contact resistance testing and data recording. After the testing is completed, the next cycle test continues. Specifically, in this embodiment, high - temperature (three temperatures A℃, B℃, C℃) aging without power - underwater power on - underwater plug and unplug 3 times without power - underwater static can be used as a cycle. It should be noted that: the air (oxygen) stress mainly means that the rubber material will undergo an oxidation reaction in an oxygen - containing environment, resulting in the hardening of the rubber, and this process will be accelerated under high - temperature conditions. The plug - and - unplug mechanical stress mainly means that during the test profile, the test piece is plugged and unplugged underwater, which will accelerate the wear of the test piece plating and the aging of rubber.

[0067] Before the reliability test, a performance test is carried out on all test specimens and the initial values are recorded. Subsequently, according to the test profile of the reliability test plan, after each completion of a test profile cycle, it is stipulated as a test period, and a performance test is carried out to record the change in the key performance (contact resistance) of the connector. After each cycle of testing is completed, the test continues until the product fails or reaches the specified cut - off condition.

[0068] Carry out multiple groups of reliability tests according to the mission profile, conduct contact resistance tests in the prescribed test cycle and calculate the contact resistance degradation amount based on the initial value;

[0069] Step 3: After the test in step 2 is completed, the acquired test data is post-processed;

[0070] In step three, the contact resistance degradation amount is obtained by subtracting the initial contact resistance value from the actual contact resistance value obtained in step two.

[0071] Step 4: Select product feature data, test data from step 2, and post-processing data from step 3 according to different needs to perform fitting and deduction to complete product reliability evaluation.

[0072] In step 4, the corresponding evaluation data is used as the conclusion according to the different usage requirements of the product, or the reliability evaluation result with a shorter calendar life is selected as the reliability evaluation of the product.

[0073] In this step, the working cycle life N of the product under a specific coating thickness THK is predicted according to the following formula, and the reliability evaluation based on the contact coating thickness THK is completed:

[0074] After knowing the corresponding relationship between the coating thickness THK and the characteristic life N, the data fitting method can be used to obtain that under a specific failure threshold (contact resistance degradation amount), the characteristic life N of the rubber-plastic watertight connector and the coating thickness THK of the contact part present a logarithmic relationship;

[0075] N=aln(THK)+b (1)

[0076] Where N is the number of underwater power-on working cycles, that is, the characteristic life of the rubber-plastic watertight connector; THK is the thickness of the contact coating; a and b are constants obtained when deriving the equation for the fitting curve, which are obtained by fitting based on the test data.

[0077] Specifically, according to Figure 2 The task profile shown carries out reliability tests on multiple groups of product samples with different contact coating thicknesses. The contact resistance of the product test pieces is tested in the reliability test according to the test cycle, and the contact resistance degradation is calculated based on the initial value of the contact resistance and the measured value of the contact resistance. Under a given failure threshold (contact resistance degradation), the characteristic life N of the product under different coating thicknesses THK can be obtained by extrapolating the test data. After the corresponding relationship between the coating thickness THK and the characteristic life N is known, the data fitting method can be used to obtain that under a specific failure threshold (contact resistance degradation), the characteristic life of the rubber-plastic watertight connector (the number of underwater power-on working cycles N / times) and the contact coating thickness (THK / μm) show a logarithmic relationship. That is:

[0078] N = a ln(THK) + b (1)

[0079] Where a and b are constants obtained when deriving the formula for fitting the curve. According to the above formula, the working cycle life of the product at a specific coating thickness can be predicted, and the reliability evaluation based on the contact part coating thickness can be completed.

[0080] In this step 4, the calendar life of the product is predicted according to the acceleration model, and the reliability evaluation based on the rib seal size is completed.

[0081] Specifically, as shown in the figure, the rib seal size at the mating part refers to the mating degree at the pinhole seal after the product is mated, which is expressed by the seal compression rate:

[0082]

[0083] Where V 插针 is the volume of the male contact part before mating (excluding the protruding part of the male contact) within the indicated rectangular box in the figure, and V 插孔 is the volume of the female contact before mating within the indicated rectangular box in the figure.

[0084] In order to utilize the product life information in the performance degradation model of the product under the temperature acceleration stress level and extrapolate the calendar life of the product under normal stress, the Arrhenius model is adopted as the acceleration model to calculate the calendar life of the product.

[0085] According to Figure 3 the shown test profile, reliability tests of multiple comparison groups are carried out at different temperatures T and different compression rates x. The contact resistance is tested during the specified test cycle, and the contact resistance degradation amount is calculated based on the initial value of the contact resistance.

[0086] The test data of the sample with a seal compression rate of x is analyzed, and a power function is used for data fitting to obtain the degradation model of the contact resistance degradation amount and time at different temperatures:

[0087] r = a * t b

[0088] Where r is the contact resistance degradation amount, t is the test time, and a and b are constants obtained by fitting according to the test data;

[0089] Substituting the determined failure threshold into the above formula for r can obtain the calendar life value t of the product at different temperatures. Based on this, the corresponding relationship between the temperature T and the calendar life value Lx is obtained, and then the corresponding relationship is substituted into the Arrhenius acceleration model to obtain the relationship model between the calendar life Lx of the product and the environmental temperature T.

[0090]

[0091] Wherein, Lx is the calendar life of the rubber and plastic watertight connector when the sealing compression rate is x. a and b are constants obtained when deriving the formula for fitting the curve, and specific values are calculated by substituting them into the Arrhenius model according to the corresponding relationship between temperature and calendar life values.

[0092] Based on the reliability test data of product test pieces with different compression rates, different acceleration models can be obtained. According to the acceleration model, the calendar life Lx of the product is predicted to complete the reliability evaluation based on the rib seal size.

[0093] This method establishes a relationship model between two key design factors and characteristic life indexes (number of working cycles, calendar life) to evaluate the reliability level of the product. According to different usage requirements of the product, the corresponding evaluation data are used as the conclusion, or the earlier of the two evaluation data is used for determination.

[0094] This solution provides a reliability evaluation method for rubber and plastic watertight connectors improved based on potential failure analysis and key design factors. This method determines the weak links of the product through FMECA, analyzes the failure mechanism for the weak links, and determines the reliability test profile according to the actual usage environment. Simulating the actual usage environment of the product, the accuracy of the evaluation result is higher and the result is more credible. According to different usage requirements of the product, the corresponding evaluation data are used as the conclusion, or the reliability evaluation result with a shorter calendar life is selected as the reliability evaluation of the product. Since the two evaluation models correspond to two key design factors, through this method, the reliability levels under different levels of the two key factors of coating thickness and rib seal size can be determined, and the appropriate design values can be selected accordingly, providing an improvement direction and suggestions for the design of the product.

[0095] In an embodiment of the present invention, a reliability prediction and evaluation system for rubber and plastic watertight connectors is also provided, which predicts the reliability state of the future product test pieces based on the test data obtained from different test pieces under specific test profiles according to different key design factors. The reliability prediction system includes:

[0096] Including a contact resistance detection unit; used to obtain the initial value of the contact resistance of the product test piece and obtain the measured value of the contact resistance of the product test piece in each cycle test period;

[0097] A contact resistance degradation amount calculation unit; used to calculate the contact resistance degradation amount through the initial value of the contact resistance and the measured value of the contact resistance;

[0098] A formula derivation unit;

[0099] For the coating thickness factor of the contact part;

[0100] Data is marked and analyzed for the contact resistance degradation amount and the number of cycles, and a linear function is used to fit the contact resistance degradation amount and the characteristic life value to derive an expression representing the fitting straight line;

[0101] Based on the failure threshold of the given contact resistance degradation amount,

[0102] According to the expression of the above fitting straight line, the characteristic life values corresponding to different coating thicknesses are calculated;

[0103] Data is marked and analyzed for different coating thicknesses and the corresponding characteristic life values, and a logarithmic function is used to fit the coating thickness and the corresponding characteristic life values to derive an expression (1) representing the fitting curve;

[0104] Through the expression (1) of the above fitting curve, the characteristic life value when the product reaches the failure threshold of the contact resistance degradation amount at different coating thicknesses can be calculated; thus, the appropriate coating thickness can be selected according to the product grade requirements, and the reliability prediction and evaluation of the product based on the coating thickness are completed accordingly.

[0105] Regarding the rib sealing size factor at the mating part;

[0106] Obtain the test time of the product at different environmental temperatures under different compression ratios;

[0107] Data is marked and analyzed for the test time and the corresponding contact resistance degradation amount at different environmental temperatures under different compression ratios, and a power function is used to fit the test time and the contact resistance degradation amount to derive an expression representing the fitting curve;

[0108] Through the above expression, the calendar life value of the product based on a specific environmental temperature under the failure threshold of the given contact resistance degradation amount can be calculated;

[0109] Substitute the specific environmental temperature and the calendar life value into the acceleration model to obtain an expression (2) for the relationship between the environmental temperature and the calendar life value at different compression ratios;

[0110] Through the above relationship expression (2), the calendar life values of the product at different environmental temperatures under different compression ratios can be calculated; by comparing the characteristic life values of the product at different compression ratios under a specific environmental temperature, the appropriate compression ratio can be selected to complete the reliability prediction and evaluation of the product based on different rib sealing sizes.

[0111] The following is an example according to specific embodiments:

[0112] Based on the coating thickness test of the specimen

[0113] The test pieces are divided into three groups according to different coating thicknesses of the specimen pieces, such as Figure 2As shown, the same test profile is set for each group to conduct the "underwater static - underwater power - on - underwater plug and unplug 10 times" cycle. The specified test period is one cycle of the test profile, that is, after each cycle is completed, the test piece is taken out for contact resistance performance testing and the measured value is recorded. The test is terminated when the product fails or the degradation amount of the test value reaches the specified threshold range.

[0114] First, place the test piece in a simulated seawater solution (3.5% salinity), let it stand still for 48 h. After standing still, connect a DC power supply to apply a rated current of 8 A. After 24 h of current conduction, stop power supply and place the test piece underwater for plugging and unplugging 10 times. After plugging and unplugging, start testing the contact resistance. This is one cycle group.

[0115] Group the test pieces according to the coating thickness. After grouping, put all grouped connectors into the simulated seawater solution according to the test profile to carry out the cycle test. After each cycle is completed, the test piece needs to be taken out for contact resistance testing and data recording. After the testing is completed, continue with the next cycle test.

[0116] After the test is completed, fit the test values to obtain the relationships between the degradation amounts of three different coating thicknesses THK n and the number of cycles t as follows:

[0117] r a = a1 + b1t (3)

[0118] r b = a2 + b2t (4)

[0119] r c = a3 + b3t (5)

[0120] In equations (3), (4), and (5), a1, b1, a2, b2, a3, and b3 are constants (obtained by fitting the test data), and t is the number of cycles. Take the failure threshold (contact resistance degradation amount) r = c (mΩ), where r is r a , r b or r c . According to the above equations (3), (4), and (5), the number of cycles (i.e., the characteristic life) when the product reaches the failure threshold under different coating thicknesses can be calculated.

[0121] According to THK1, THK2, THK3 and their corresponding number of cycles, logarithmic distribution fitting gives the following equation:

[0122] N = aln(THK) + b (1)

[0123] Where a and b are both constants. According to the above formula, the number of product working cycles N (i.e., the characteristic life) can be calculated by inputting the coating thickness THK. Based on this, the appropriate coating thickness THK can be selected according to the product grade, and thus the reliability evaluation of the product based on the coating thickness is completed.

[0124] According to the test results of the contact resistance, after the test, we fitted the test values to obtain the THK of three different coating thicknesses n The relationships between the degradation amounts of (1.5μm, 3.5μm, 5.5μm) and the number of cycles t are as follows:

[0125] r 1.5 = 0.04298 + 0.007913t

[0126] r 3.5 = 0.01365 + 0.006938t

[0127] r 5.5 = 0.02973 + 0.007687t

[0128] Where r is the contact resistance degradation amount and t is the number of cycles. Taking the failure threshold as 0.6 (mΩ), according to the above formula, the number of cycles (i.e., the characteristic life) when the product reaches the failure threshold under different coating thicknesses can be calculated as 70.39, 84.51, 74.19 (times) respectively.

[0129] Based on THK1 = 1.5μm, THK2 = 3.5μm, THK3 = 5.5μm and their corresponding 70.39, 84.51, 74.19 (times), logarithmic distribution fitting gives the following formula:

[0130] N 0.6 = 4.689ln(THK) + 71.11

[0131] Where N 0.6 is the characteristic life when the failure threshold is 0.6mΩ. According to the above formula, the number of product working cycles (i.e., the characteristic life) can be calculated by inputting the coating thickness. Based on this, the appropriate coating thickness can be selected according to the product grade, thus completing the reliability evaluation of the product based on the coating thickness.

[0132] Based on the rib seal size test

[0133] The test pieces are divided into three groups according to different rib seal sizes, such as Figure 3As shown, the same test profile is set for each group to conduct the cycle of "aging without power-on at high temperature (three temperatures: 70°C, 95°C, 115°C) - power-on underwater - plugging and unplugging underwater - static placement underwater". The specified test cycle is one cycle of the test profile, that is, after each cycle is completed, the product test pieces are taken out for contact resistance performance testing and the measured values are recorded. The test is terminated when the product fails or the degradation amount of the test value reaches the specified threshold range.

[0134] Performing power function regression fitting on the test data can obtain the contact resistance degradation models of the product test pieces under three temperatures and three compression ratios, as Figure 5 shown;

[0135] Substituting the failure threshold of the given contact resistance degradation amount into the degradation model can calculate the calendar life Lx of the product at different temperatures; as Figure 6 shown:

[0136] Regarding the reliability test of the rib seal size. Since the test period is long and the cost is high at room temperature, a high-temperature accelerated test method is adopted to shorten the reliability test period. The product test pieces under each compression ratio in the high-temperature accelerated test are divided into three groups and tested in high-temperature environments of 70°C, 95°C, and 115°C respectively. The test simulates the conventional use requirements of the product and adds high-temperature stress as the acceleration stress to establish the test profile as Figure 3 , that is, the process of "aging without power-on at high temperature (three temperatures: 70°C, 95°C, 115°C) - power-on underwater - plugging and unplugging underwater - static placement underwater".

[0137] First, the test pieces are placed in high-temperature ovens (70°C, 95°C, 115°C) according to the grouping for high-temperature aging. For example, when the aging times reach 48h, 192h, 500h, 800h, 1000h, 1300h, and 1500h respectively, they are taken out from the temperature chamber and randomly placed in a seawater solution (3.5% salinity) to connect a DC power supply to pass a rated current of 8A. After 24h of current passing, the power supply is stopped, and the test pieces are placed underwater for plugging and unplugging 3 times. After the plugging and unplugging are completed, they are statically placed in the seawater solution for 24h, and then the contact resistance is tested. After the plugging and unplugging are completed, the contact resistance is tested, and this is 1 cycle group.

[0138] As shown in Table 1:

[0139] Table 1 Contact resistance fitting degradation models at different temperatures for different compression ratios

[0140]

[0141] Substituting the failure threshold of the contact resistance degradation amount of 1.6 (mΩ) into the degradation model can calculate the calendar life Lx of the product at different temperatures as shown in Table 2:

[0142] Table 2 Calendar life based on the degradation model

[0143]

[0144] Using the Arrhenius equation acceleration model, substitute the above table values into the acceleration model to obtain overdetermined equations at three compression ratios:

[0145]

[0146] By solving using the least squares method to obtain the values of a and b, the relationship model between the life of the product based on the degradation of contact resistance and the ambient temperature is:

[0147]

[0148]

[0149] According to the above formula, the characteristic life L of the product at different compression ratios can be calculated by inputting the working ambient temperature value T. The reliability levels of the three sealing sizes at the working ambient temperatures of 30°C and 50°C are:

[0150] Table 3 Evaluation of the reliability study of the rib based on contact resistance

[0151] Standard circular compression ratio Life at 30°C (a) Life at 50°C (a) 3％ 1.57 1.61 8％ 33.9 13.4 14％ 33.8 9.9

[0152] Select a suitable compression ratio by comparing the characteristic life values of the product at different compression ratios. The initial compression ratio of the product is 20%. According to this method, the compression ratio with the longest characteristic life is calculated to be 8%. Based on this, the rib size compression ratio of the product is improved to 8% to increase the characteristic life of the product, and the reliability evaluation and design based on the rib size are completed.

[0153] Parts not detailed in this solution are all prior arts.

[0154] The above are only preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the equivalent embodiments of equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A reliability evaluation method for a rubber-plastic watertight connector, which predicts the reliability status of the product test piece in the future according to the test data obtained from the product test piece under a specific test profile based on different key design factors. The reliability evaluation method is characterized in that: the initial value of the contact resistance of the product test piece is obtained and the actual measured value of the contact resistance of the product test piece is obtained in each cycle test period, the contact resistance degradation amount is calculated by the initial value of the contact resistance and the actual measured value of the contact resistance, and the characteristic parameters of the product test piece based on different key design factors and the corresponding related data obtained are marked and analyzed, and a prescribed function is used to derive a formula representing the marked fitting line or fitting curve.

2. A reliability evaluation method for a rubber-plastic watertight connector according to claim 1, characterized in that: The reliability status of the product test pieces in the future is predicted based on the test data obtained under the respective specific test profiles for the two key design factors, namely the contact plating thickness of the product test pieces and the rib sealing size of the product test pieces at the insertion part; the initial contact resistance values ​​of all product test pieces are obtained, and all grouped product test pieces are placed in a simulated test solution for cyclic testing based on the key design factors and in accordance with the corresponding set test profiles. After each cycle of testing is completed, the next cyclic test is continued until the product test piece fails or reaches the failure threshold of a given contact resistance degradation amount.

3. The reliability evaluation method of a rubber-plastic watertight connector according to claim 1 is characterized in that: In the reliability evaluation method; Plating thickness factor for contacts; By obtaining the initial value of contact resistance and the measured value of contact resistance, the contact resistance degradation amount is calculated, and the contact resistance degradation amount and characteristic life value of the product under different coating thicknesses are obtained. By marking and analyzing the data of the contact resistance degradation amount and the number of cycles, and fitting the contact resistance degradation amount and the characteristic life value with a linear function, a formula representing the fitting straight line is derived; The failure threshold based on a given amount of contact resistance degradation is The characteristic life values ​​corresponding to different coating thicknesses are calculated based on the above fitting straight line formula; By performing data labeling analysis on different coating thicknesses and corresponding characteristic life values, and fitting the coating thicknesses and corresponding characteristic life values ​​with a logarithmic function, equation (1) representing the fitting curve is derived; The above fitting curve formula can be used to calculate the characteristic life value of the product when it reaches the failure threshold of the contact resistance degradation amount at different coating thicknesses; Therefore, the appropriate coating thickness can be selected according to the product grade, and the reliability prediction evaluation of the product based on the coating thickness can be completed accordingly.

4. The reliability evaluation method of a rubber-plastic watertight connector according to claim 1 is characterized in that: The characteristic life is the number of cycles.

5. A reliability evaluation method for a rubber-plastic watertight connector according to any one of claims 2 to 4, characterized in that: In the reliability evaluation method; According to the rib seal size factor at the insertion part, the compression rate of different rib seal sizes is calculated; The contact resistance degradation amount is calculated by obtaining the initial value of the contact resistance and the measured value of the contact resistance; Obtain the test time of the product at different ambient temperatures and at different compression rates; By performing data marking analysis on the test time and the corresponding contact resistance degradation at different ambient temperatures with different compression ratios, and fitting the test time and the contact resistance degradation with a power function, a formula representing the fitting curve is derived; The above formula can be used to calculate the calendar life value of the product at a specific ambient temperature under the failure threshold of a given contact resistance degradation amount; Substituting the specific ambient temperature and calendar life value into the acceleration model, the relationship between the ambient temperature and the calendar life value under different compression rates is obtained (2); Through the above relationship (2), the calendar life value of the product at different ambient temperatures with different compression rates can be calculated; By comparing the characteristic life values ​​of products with different compression rates at specific ambient temperatures, the appropriate compression rate can be selected to complete the reliability prediction evaluation of the product based on different rib seal sizes.

6. A reliability evaluation method for a rubber-plastic watertight connector according to claim 5, characterized in that: According to the reliability prediction evaluation results based on the coating thickness and the reliability prediction evaluation results based on different rib sealing sizes, the corresponding reliability prediction evaluation results can be used as conclusions based on different usage requirements, or the first of the two reliability prediction evaluation results can be used as the final reliability prediction judgment standard for the product.

7. A reliability prediction program for a rubber-plastic watertight connector according to claim 3 or 4, characterized in that: The formula (1) is expressed as: N=aln(THK)+b (1) In formula (1), N is the characteristic life of the rubber water-sealed connector; THK is the contact coating thickness; a and b are constants obtained when deriving the equation for the fitting curve.

8. The reliability prediction program of a rubber-plastic watertight connector according to claim 5, characterized in that: The formula (2) is expressed as: In formula (2), L x is the calendar life of the rubber-plastic watertight connector when the sealing compression rate is x; T is the ambient temperature value, and a and b are the constants obtained when deriving the formula for the fitting curve.

9. A reliability evaluation system for rubber-plastic watertight connectors, which predicts the reliability status of the product test pieces in the future based on different key design factors and test data obtained from different test pieces under specific test sections, wherein the reliability prediction system is characterized by: It includes a contact resistance detection unit; used to obtain the initial value of the contact resistance of the product test piece and obtain the actual measured value of the contact resistance of the product test piece in each cycle test period; A contact resistance degradation amount calculation unit; used to calculate the contact resistance degradation amount according to the initial contact resistance value and the contact resistance measured value; Formula export part; Plating thickness factor for contacts; By marking and analyzing the data of the contact resistance degradation amount and the number of cycles, and fitting the contact resistance degradation amount and the characteristic life value with a linear function, a formula representing the fitting straight line is derived; The failure threshold based on a given amount of contact resistance degradation is The characteristic life values ​​corresponding to different coating thicknesses are calculated based on the above fitting straight line formula; By performing data labeling analysis on different coating thicknesses and corresponding characteristic life values, and fitting the coating thicknesses and corresponding characteristic life values ​​with a logarithmic function, equation (1) representing the fitting curve is derived; Regarding the rib seal size factors at the insertion part; Obtain the test time of the product at different ambient temperatures and at different compression rates; By performing data marking analysis on the test time and the corresponding contact resistance degradation at different ambient temperatures with different compression ratios, and fitting the test time and the contact resistance degradation with a power function, a formula representing the fitting curve is derived; The above formula can be used to calculate the calendar life value of the product at a specific ambient temperature under the failure threshold of a given contact resistance degradation amount; The specific ambient temperature and calendar life value are introduced into the acceleration model to obtain the relationship between the ambient temperature and the calendar life value under different compression rates (2).

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